Added a bean module in pelix.shell

Defines the classes used by the Pelix shell v2 and its consumers:
- IOHandler: the I/O handler, like in Pelix shell v1
- ShellSession: Stores session variables
Pelix shell core, console and remote use the new beans

Added set and unset methods
Added support for $var and ${var} in command line arguments (see string.Template)
Removed Eclipse project files from repo